This invention relates to azeotropic or azeotrope-like compositions containing 1-chloro-2,2-difluoroethane (xe2x80x9cHCFC-142xe2x80x9d or xe2x80x9c142xe2x80x9d) which can be used in various applications such as the cleaning, drying, degreasing and dry cleaning of solid surfaces (particularly defluxing and cold cleaning of printed circuits), in aerosol applications, and as foam blowing agents, particularly to such compositions wherein the 142 is blended with methanol, 1,1,1,3,3-pentafluorobutane (xe2x80x9cHFC-365 mfcxe2x80x9d or xe2x80x9c365 mfcxe2x80x9d or xe2x80x9c365xe2x80x9d) or mixtures thereof.
1,1,2-Trichloro-1,2,2-trifluoroethane (xe2x80x9c113xe2x80x9d) and 1,1,1-trichloroethane (xe2x80x9c140axe2x80x9d) have been widely used in industry as cleaning solvents for many years. However, they have been suspected to cause depletion of the stratospheric ozone layer and were banned by the Montreal Protocol. 1,1-Dichloro-1-fluoroethane (xe2x80x9c141bxe2x80x9d) has been used to replace these solvents, as well as being widely used as a foam blowing agent, but it, too, is being banned because of its relatively high ozone depletion potential (xe2x80x9cODPxe2x80x9d). These three solvents were used, among other things, for metal degreasing, removing solder flux from electronic components, and precision cleaning of sensitive equipment, such as gyroscopes. Their boiling points made them useful for aerosol or cold cleaning. Solvents proposed to replace these are often flammable (such as the 365/methanol mixtures of U.S. Pat. No. 5,268,121) or have low solvent power (such as perfluoro- carbons). It would thus be useful to find replacements which avoid these problems.
As used in this application, the term xe2x80x9cazeotrope-like compositionsxe2x80x9d refers to mixtures or blends of generally miscible chemical compounds which boil at a substantially constant temperature while at the same time remaining substantially the same composition. When heated to reflux, such an azeotrope-like composition is in equilibrium with a vapor phase whose composition is substantially the same as that of the liquid phase. Such behavior is desirable to ensure satisfactory functioning of the machines in which cleaning operations are carried out, such as recycling by distillation.
Herein provided, among other things, are azeotropic or azeotrope-like compositions comprising, on a weight basis, (a) about 50-90% of 142 with about 50-10% of 365 (preferably 60-80% of 142 with 40-20% of 365); (b) about 91-99.5% of 142 with about 9-0.5% of methanol (preferably 93-99% of 142 with 7-1% of methanol); and (c) about 50-75% of 142 with about 25-45% of 365 and about 0.5-10% of methanol (preferably 55-65% of 142 with 30-40% of 365 and 1-7% of methanol), methods for using the same for cleaning or drying of solid surfaces or as a foam blowing agent, specific azeotropic compositions of the foregoing mixtures (about 71.5% of 142 and about 28.5% of 365, which composition has a boiling point of about 35.4xc2x0 C. at normal atmospheric pressure (about 1.013 bar); about 95.9% of 142 and about 4.1% of methanol, which composition has a boiling point of about 34.7xc2x0 C. at normal atmospheric pressure; and about 62% of 142 plus about 3.6% of methanol and about 34.4% of 365, which composition has a boiling point of about 33.9xc2x0 C. at normal atmospheric pressure), and the like.
Azeotropic and azeotrope-like compositions of 142 with 365, methanol or mixtures thereof have now been identified which solve many of the foregoing problems. The ODP of 142 is 0.02, compared to 0.8, 0.1 and 0.1 for 113, 140a, and 141b, respectively. HFC-365 and methanol have a zero ODP. Furthermore, these compositions have no flash point (using standard determination conditions, ASTM standard D 3828), making them safer for their intended use.
The inventive compositions can be readily prepared by simple mixing of the constituents.
As with prior cleaning compositions based on 113 or 141b, the cleaning compositions of this invention can, if so desired, contain stabilizers to protect against chemical attack resulting from their contact with water (hydrolysis), with light metals (constituting the solid surfaces to be cleaned) and/or against radical attacks liable to occur in the cleaning process. Exemplary of such stabilizers are nitroalkanes (such as nitromethane, nitroethane, or nitropropane), acetals (such as dimethoxymethane or dimethoxyethane) and ethers (such as 1,3-dioxolane or 1,4-dioxane). The proportion of stabilizer typically ranges from about 0.01 to about 5% based on the total weight of the composition. Dimethoxymethane is a preferred stabilizer.
The inventive compositions are particularly suitable for use in cleaning and degreasing of solid surfaces, particularly in defluxing of printed circuits, as well as in operations for drying surfaces, all according to conventional means, including aerosol application. They are useful as blowing agents for polyurethane foams, the foam formulation containing polyisocyanate, polyol and blowing agent and being made by conventional means. Other applications include use as refrigeration fluids and as dry-cleaning agents for textiles.